JPS5819764B2 - Boshuyouyouekinoseizohou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a spinning solution of an acrylonitrile-based polymer, and more particularly to a method for producing a spinning solution from a wet acrylonitrile-based polymer produced by aqueous precipitation polymerization. It is about the method.

Generally, water is used in the production method of IJ-based polymers, but this is because water, which corresponds to the solvent, is cheap;
The reaction rate in the precipitated polymer, where the produced polymer precipitates into the aqueous phase and the monomer is sorbed, is compared to the reaction rate in the homogeneous phase where acrylonitrile, the main component of the monomer, is dissolved in water. It is fast and has high productivity compared to reactions in organic solvents such as dimethylformamide and dimethyl sulfoxide, and it also uses azobis-based organic catalysts that are soluble in monomers as well as redox initiators that are soluble in water. This is because the catalyst can be used in a wide range of applications, and has many other industrially favorable features such as removal of reaction heat, reduction in reaction liquid viscosity, and separation of produced polymers.

In order to produce a spinning solution from this wet acrylonitrile polymer, the water content of the solution must be 3% by weight or less.

This is because if the moisture content exceeds 3% by weight, problems such as blockage of the spinning nozzle hole, decrease in stretching ratio, gelation of the solution, formation of voids in the system, devitrification of the yarn, and instability of the yarn quality occur. This is because it causes harm.

Conventionally, methods for reducing the water content of a solution produced from a wet polymer containing approximately 30% by weight or more of water to 3% by weight or less include a drying method using a simultaneous heat and mass transfer phenomenon, or a mass transfer phenomenon using a solvent. Methods for removing water in a solid state, such as a water extraction method using water, are known.

In either case, some of the water in the solution is free, but some of the water is sorbed and occluded within the micropores of the aggregated particles of polymer chains, which are in a porous state. Therefore, first, the free water in the aggregated particles is evaporated from the surface of the micropores by constant rate drying, and then the moisture in the pores is also evaporated by lapse rate drying, and the sorbed and occluded water is removed. needs to be evaporated.

According to this method, the heat loss during the constant rate drying period is small, whereas the lapse rate drying has a low heat loss during the period corresponding to the second stage of the lapse rate, in which the sorbed and occluded water is evaporated. The heat loss is particularly high, and some of the polymers are exposed to high temperatures during drying, resulting in white discoloration and reduced thermal stability. Similarly, when water is extracted with organic solvents, free water must be removed. Although easy to extract, it is very difficult to extract the water absorbed and occluded in solids, and the lapse rate is 10 to 15 based on the polymer equivalent to the first stage.
%, and it is almost impossible industrially to reduce the water content in the system to 3% or less while the polymer particles are suspended.

In order to improve these drawbacks, the present inventors suspended wet polymer particles containing water in a spinning solvent, and under reduced pressure, the particles were freed from adsorption or occlusion, that is, free water. A method of distilling off non-solvent water and monomers, then dissolving the polymer in a solvent after raising the temperature, and distilling the sorbed and occluded water out of the solution under reduced pressure, Japanese Patent Application No. 1973- 11532
I proposed No. 8.

However, in this method, water and the monomer as a non-solvent escape from the polymer particles from the suspended state where the polymer particles are dispersed in a solvent in an undissolved state, and the dispersed polymer is completely dissolved. The process of transitioning to a homogeneous solution state, that is, the operation in an incompletely dissolved state until some of the polymer particles begin to dissolve and the entire polymer particles dissolve, takes a long time, which poses some industrial problems for reasons explained later. occurs.

That is, the history from a completely undissolved state in which polymer particles are dispersed in a solvent in an undissolved state to a completely dissolved state in which they are uniformly dissolved can be explained using a composition diagram of a polymer solution as follows.

Point W in the figure indicates a composition of 100% water, point S indicates a composition of 100% solvent, and point P indicates a composition of 100% polymer.

The figure is a composition diagram of a three-component system of water and solvent dipolymer. In the figure, the phase states according to the polymer composition are divided into points W, A, and B.

The line connecting points P is a completely undissolved zone where no polymer particles are dissolved, and the line connecting points A, B, and DtC is a completely undissolved zone where some polymer particles are dissolved but some are not. Points C and D are incompletely dissolved zones in a dissolved state.

The area within the line connecting S is a complete dissolution zone where the polymer is completely dissolved.

Also, a spot in the incomplete dissolution zone, E. A portion of the polymer is dissolved within the line connecting F, but this is a gelation zone where the dissolved polymer solidifies due to branching, crosslinking, etc., and becomes a gel state.

The purpose of Japanese Patent Application No. 49-115328 is to add a solvent to a water-containing polymer (two stages), i.e., point I in the figure, to obtain the composition of point 1, and distill off the solvent and water under reduced pressure to form one point. A spinning solution with the desired composition at point T is produced by processing along the operating line shown by the chain line from point 1 to the composition at point T in two stages, one in which the polymer is dispersed and one in which the polymer is dissolved. There was something to do.

When changing the composition from operating point 1 to target point T, it is essential to pass through an incomplete dissolution zone, which is the main cause of concentration unevenness, which will be described later, and depending on the conditions, a gelation zone may occur.

The main problems encountered in industrialization at this time are described below.

(i) Density unevenness occurs in the obtained spinning solution.

The cause of this is that water and monomer adsorbed and absorbed in the pores of the aggregated polymer are removed in the incomplete dissolution zone, and the polymer is gradually dissolved by replacing it with a solvent. This is thought to be due to the fact that the vicinity of the surface of the particles, which is easy to dissolve, dissolves first, and water or monomers inside the particles become difficult to remove, resulting in uneven concentration in a part of the polymer.

Furthermore, when the solution passes through a gelation zone, a gelation product is generated in the solution.

(ii) Filtration pressure increases and becomes unstable.

During long-term continuous operation, the concentrated particles gradually clog the f-material, and the filtration pressure of the f-filter in front of the spinning machine increases with the operating time, causing problems in continuous stable operation over a long period of time. arise.

(11i) Decreases spinnability.

As described in the example of Japanese Patent Application No. 115328/1984,
In the early stages of continuous operation on a small-scale device, there were no problems with spinnability, but depending on the preparation conditions, as the operation time became longer and the device was expanded, yarn breakage occurred during spinning and cleaning, and the resulting It has become clear that there are cases in which the yarn is unsuitable for industrial use, as it causes uneven fineness.

This is related to the above-mentioned increase in filtration pressure, and the uneven concentration of the polymer is thought to be the underlying cause.

(IV) The range of operating conditions is narrow, making it difficult to obtain a stable polymer solution.

When changing the composition from operating point 1 to the desired operating point T on the operating diagram, an incomplete dissolution zone is observed, but this operating line is constrained by the gelation zone, and the range of operating conditions becomes very narrow, resulting in a slight dissolution zone. Since gelled products are also generated due to disturbances in the temperature, it becomes difficult to obtain a stable polymer solution as the equipment becomes larger.

(V) Restrictions on the device become stricter.

In the incomplete dissolution zone, where a part of the polymer is dissolved and a part is undissolved, the viscosity rapidly increases, and depending on the conditions, it becomes impossible to mix.

As a result, heat transfer efficiency decreases, and due to factors such as the need for long-time heating to complete melting, industrial equipment becomes extremely complex, and the size of the equipment per polymer throughput becomes extremely complex, especially in terms of heat transfer and melting time. The productivity is limited and the productivity per device is reduced.

As described above, the technique disclosed in Japanese Patent Application No. 115328/1983 has obtained good results, but when it comes to industrialization, there are various problems such as narrow control range, etc., and it is difficult to stably produce a spinning solution. It became clear that there were still many points that needed to be improved in order to achieve this goal.

The inventors of the present invention have made extensive studies to improve these drawbacks, and as a result have come up with the following improved method.

That is, the present invention takes an acrylonitrile polymer containing a large amount of water obtained by aqueous precipitation polymerization, adds a solvent to the polymer, and then distills off the water under reduced pressure, or distills the water from the polymer under pressure. The polymer is dehydrated until the water content in the polymer reaches 3 to 50% by squeezing with water, etc., and then dissolved in a solvent for the polymer.
A method for producing a spinning solution of an acrylonitrile polymer, the method comprising obtaining a solution having a moisture content of 3% or less and a polymer concentration of 15 to 30% by weight by subjecting it to vacuum treatment at 120°C and 500 to 0.1 torr. It is related to.

The most important point of this invention is that some of the polymer begins to dissolve;
The other method is to instantaneously treat the undissolved incompletely dissolved zone and gelled zone to cause a phase change from a completely undissolved state to a completely dissolved state.

Hereinafter, a specific method for instantaneously treating the incompletely dissolved zone and gelled zone will be explained based on some examples, focusing on the composition diagram.

Example 1 A predetermined amount of solvent is supplied to one polymer containing water to prepare two compositions, and the water and solvent are distilled off under reduced pressure to obtain three compositions.

The suspended polymer in this state is completely undissolved.

Furthermore, an amount of solvent sufficient to completely dissolve the polymer is added to the three compositions to instantaneously make the four compositions.

At point 4, the polymer is already completely dissolved.

Once again, water and solvent are distilled off under reduced pressure from point 4, and the process is carried out until the desired composition is reached at point T.

At this time, in the process from point 3 to point 4, the incomplete dissolution zone and gelation zone are instantaneously transferred, thereby eliminating density unevenness.

Example 2 A wet polymer with a composition of 1 point is removed with a compressor with a good squeezing rate, a squeezer, etc. to make a composition of 5 points, and the weight of the wet polymer with a composition of 5 points is Add a sufficient amount of solvent to completely dissolve the coalesce, and instantly form a 6-point composition.

In the composition of 5 points, the polymer is not dissolved at all, but in the composition of 6 points, the polymer is completely dissolved in the solvent.

Furthermore, water and solvent are distilled out under reduced pressure from point 6 to obtain the desired composition point T.

At this time, in the process of transitioning from the 5-point composition to the 6-point composition, concentration unevenness does not occur (no longer occurs) by instantaneously passing through the incomplete dissolution zone and the gelation zone.

These are typical examples of instantaneous history of incomplete dissolution zones and gelation zones, and it is natural that there are various other methods.

The present invention will be further explained.

Among the organic solvents known as solvents for acrylonitrile-based polymers, the solvents used in the present invention have a boiling point higher than that of water, and specific examples thereof include:
N as an amide compound.

N-dimethylformamide, N,N dimethylacetamide, N-methylpyrrolidone, N,N-dimethylmethoxyacetamide, N,N,N',N'.

Tetramethyloxyamide, benzyldimethylamide,
N, N, N', N'-tetramethylphthalamide,
ε-caprolactam, 2-oxazolidone, N-formylhexamethyleneimino, N,N'-diformylpiperazine, 4-formylmorpholine, N-formylpyrrolidine, N-formylpiperidine, 4-acetylmorpholine, 4-acetylpyrrolidine, Arononitrile, succinonitrile, adiponitrile, bis(β-cyanocochel)ether, bis(β-cyanoethyl sulfide), sulfone as a nitrile compound, and dimethyl sulfoxide as a sulfoxide compound.

Dimethylsulfone, ethylmethylsulfone, sulfolane, thiocyanate compounds such as methylene dithiocyanate, trimethylene dithiocyanate, nitro compounds such as m- or P-nitrophenol, 4-nitrosomorpholine, phosphorus compounds such as tris(dimethylamide) phosphate, γ-butyrolactone as a carbonate compound.

Examples include ethylene carbonate.

Among these, dimethylacetamide, dimethylformamide, dimethyl sulfoxide and the like are particularly preferred solvents for the purpose of the present invention.

The polymer used in the present invention is not only a polymer of acrylonitrile alone, but also a copolymer of 50% by weight or more of acrylonitrile and other copolymerizable monomers.

Examples of copolymerizable monomers include ethylenically unsaturated compounds, vinyl acetate, ethyl acrylate, methyl acrylate, and methyl methacrylate.

Methacrylonitrile, methylene geltalonitrile.

Examples include vinyl bromide, vinyl chloride, vinylidene chloride, acrylamide, N,N'-substituted acrylamide, methacrylamide, acrylic acid, and methacrylic acid.

Of course, it also includes copolymers in which appropriate amounts of basic or strongly acidic monomers are co-electrified for the purpose of improving dyeability. Examples of such basic or strongly acidic monomers include vinylpyridines, etc. , dimethylaminoethyl acrylate, methacrylsulfonic acid or its salts, etc.

As explained above, the present invention removes water and monomers from a water-containing acrylonitrile polymer under conditions in which the polymer does not dissolve at all, and then adds a spinning solvent to form a part of the polymer. This is a new method in which the polymer is completely dissolved by instantaneously going through the so-called incomplete dissolution zone or gelation zone, where some parts are dissolved and others are not, and then the water and solvent are further distilled out under reduced pressure. According to the present invention,
(a) Concentration unevenness does not occur in the spinning solution as seen in conventional methods.

(b) Overpressure is stabilized and operability is improved.

(c) Compared to conventional methods, the operating range is wider and it is easier to obtain a stable polymer solution.

) The amount of heat used is approximately - that of a conventional drying process.

(E) Even after continuous operation for a long period of time, the quality of the thread remains stable and the operability is improved.

(f) The number of nozzle blockages and thread breakages during spinning is reduced,
Therefore, spinnability is improved.

(g) The recovery rate of harmful substances such as acrylonitrile and catalyst by-products is improved, which is preferable in terms of pollution control.

The present invention is industrially very advantageous because of the following advantages.

The present invention will be described in more detail below based on Examples.

Parts and percentages are by weight unless otherwise specified.

The Yamaga measurement is a value obtained from the reflectance of the fiber surface using a Hitachi Nikki spectrophotometer model EPU-2, and is a value when a white plate of magnesium oxide is taken as 100.

Also, the pressure unit is 1 Torr = 1 mmHg.

Example 1 A wet polymer consisting of 100 parts of a copolymer of 93% acrylonitrile and 7% vinyl acetate, 200 parts of water, and 1 part of acrylonitrile was suspended in 200 parts of dimethylacetamide and heated at 60°C and 20 torr. Under these conditions, water containing the solvent and monomer was distilled out for 60 minutes.

This was in a state where the polymer was not dissolved and the water content was 8%.

Thereafter, 500 parts of dimethylacetamide was added to completely dissolve the polymer, and then the mixture was heated at 60°C for 2 hours.
The solvent containing water and monomers was distilled off under 0 torr for 1 hour.

Analysis of the resulting solution revealed that water was 0.05% and polymer 24%.
%, and no monomer was detected.

When this solution was wet-spun using a conventional method using a spinning nozzle with 2000 holes and a hole diameter of 0.075 mm, there was almost no nozzle clogging or yarn breakage for 3 days, and the overpressure before spinning was constant.

For comparison, when the same wet polymer was subjected to aeration drying treatment and spun under the same conditions, nozzle blockage occurred within 24 hours.
There were 3 pieces, and the thread broke 2 to 4 times.

Further, the yarn bundle obtained by spinning was stretched, washed, treated with oil, dried, and subjected to relaxation treatment at 140°C, and the Yamaga was measured. The Yamaga of the fiber obtained in the present invention was 98.5. As a comparison, a wet polymer was subjected to air drying treatment, and Yamaga 94. It showed significantly higher Yamaga than O.

Example 2 300 parts of dimethylacetamide was added to a wet polymer of 100 parts of a copolymer of 93% acrylonitrile and 7% of vinyl acetate, 200 parts of water, and 1 part of acrylonitrile, and the solvent was heated at 80°C and 40 torr. Water containing monomers and monomers was distilled out for 50 minutes.

The composition at this time was such that the polymer was not dissolved at all in the solvent and the water content was 7%.

Next, after completely dissolving the polymer by adding another 500 parts of dimethylacetamide, 60°C125
The water containing the monomers and the solvent were distilled off under the conditions of 1 hour.

Analysis of the resulting solution revealed that water was 0.02% and polymer concentration was 2.
It was 3.5% and no monomer could be detected.

When this solution was wet-spun in exactly the same manner as in Example 1, 3
There was almost no nozzle blockage or yarn breakage during the day, and f in front of the spinning machine
The overpressure was also constant, and Yamaga was 98.8, which was extremely good.

Example 3 100 parts of dimethylformamide was added to a wet polymer of 100 parts of a copolymer of 93% acrylonitrile and 7% of vinyl acetate, 200 parts of water, and 1 part of acrylonitrile, and the mixture was heated at 60°C and 25 torr. The solvent containing the monomer and water were distilled off.

The composition at this time was such that no polymer was dissolved in the solvent and the water content was 15%.

After that, the polymer was completely dissolved by adding another 500 parts of dimethylformamide, and then 70°C13
Water containing monomers and the solvent were distilled off under conditions of 0 torr.

Analysis of the resulting solution revealed that water was 0.08% and polymer concentration was 2.
3%, and no monomer was detected.

When this solution was wet-spun in exactly the same manner as in Example 1, there was no nozzle clogging or yarn breakage, and the overpressure in front of the spinning machine was constant, allowing stable spinning.

The white discoloration of the obtained fiber was 93.5, indicating a significant improvement in white discoloration.

[Brief explanation of drawings]

The drawing is a diagram showing the transition of the composition of the polymer solution in the process of producing a spinning solution.

Claims (1)

[Claims] 1 An acrylonitrile polymer containing a large amount of water obtained by aqueous precipitation polymerization is dehydrated until the water content in the polymer becomes 3 to 50%, and then dissolved in a solvent for the polymer. , this solution was further heated at 30 to 120°C,
Treated under reduced pressure under conditions of 500 to 0.1 torr to reduce moisture content to 3%.
Hereinafter, a method for producing a spinning solution of an acrylonitrile-based polymer is characterized in that a solution having a polymer concentration of 15 to 30 weight percent is obtained.